2. The test to kill all three variables in one step is the F test with test stat 12.82165585 and you compare it to an $F_{3,36}$.
The p-value is $P(F_{3,36}>12.82165585)$ and the printout gives that value as 7.48476E-06.
So as long as $\alpha>7.48476E-06$, you reject $H_0$ which is that all three variables can be dropped.